The use of silica for "chillproofing" beer is well known. Reference may be had to the U.S. Pat. to McLaughlin et al No. 4,508,742 dated 2 Apr. 1985 and to the background and prior art references cited therein. Reference may also be had to U.S. Pat. Nos. 3,716,493 dated 13 Feb. 1973 and 3,959,174 to Winyall et al dated 25 May 1976 each of which discloses a method of making an ammonia aged silica.
Basically, the problem with beers, ales, lagers, and stouts is one of the tendency of these beverages to form haze or turbidity on storage. Treating the malt beverage with various kinds of silica removes or sequesters the agents responsible for haze formation at reduced temperatures to various degrees. After treatment, the silica is removed. This process is known as "chillproofing". To my knowledge, the only worker in the art who has used an ammonia treated silica for the chillproofing of malt beverages is Heimann, U.S. Pat. No. 2,316,241 dated 13 Apr. 1943.
Heimann (U.S. Pat. No. 2,316,241 dated 13 Apr. 1943) uses a gel that contains more water than the gels used in this invention. The patentee uses concentrated hydrochloric acid (the commercial product generally has 36% HCl) diluted with an equal volume of water, yielding approximately 18% acid. He neutralizes this with 40.degree. Baume waterglass solution (37% sodium silicate) which is also diluted with an equal volume of water, resulting in an approximately 18.5% sodium silicate solution. The ingredients for the gel preparation used in a specific embodiment of the present invention are 41.5% sulfuric acid and 29% sodium silicate. The resulting reaction mixture of the present invention has approximately half the amount of water compared with Heimann's mixture. Those skilled in the art know that this difference in concentration causes the solidification of a gel to take approximately ten times longer for the more dilute system. This is the reason Heimann makes his gel by one of three methods: 1. Precipitation with ammonia, or 2. by letting the mixture stand for several days or 3. by heating the mixture to 90 or 100 degrees C. The gel used in the present invention gelatinizes in 30 to 60 minutes. (Date for this difference of gelation time are given in "The chemistry of silica" by Ralph K. Iler, John Wiley & Sons, 1979, page 368). The differences in the character of gels is given by Heimann in his patent. On page one, left side line 53, he mentions that the stabilizing effect of his product "cannot be attained when employing an ordinary silica gel prepared with an acid". The gel of this invention is an ordinary silica gel prepared with acid.
Prior processes use, in general, higher amounts of silica up to 25 lbs/100 bbls of beverage.